Suzuki GSX-R 1186

FIRST KNOWN MOTORCYCLE: Daimler, late 1885. First known motorcycle drag race: sometime in early 1886, immediately after Gottlieb Daimler built the second motorcycle.
Actually, no one is certain that such a race ever took place, but common sense suggests that it probably did. After all, everyone knows what happens when two motorcycles arc in the same place at the same time: a contest of performance. Even in its infancy more than a century ago, the internal-combustion mentality was obsessed with building machines that could outrun the next guy's.

Today, despite the ready availability of phenomenally quick production motorcycles, that obsession is still alive and well. Which explains why we were inspired to take a 1991 Suzuki GSX-R1100-a bike already capable of mid-10-second E.T.s and low-130-mph terminal speeds—and tweak it into something even quicker. We just couldn't help ourselves.
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The 4-into-2-into-1 exhaust system exits through the lower fairing, ottering a clean appearance and allowing access to the oil fitter without removal of the header.

We've done GSX-Rl 100 hop-ups before, of course, but this time wc took a slightly different approach. This time our goat was to build a GSX-R1100 drag weapon that would run in the nine-second bracket while also being affordable and streetable. And in the process, wc didn't want to sacrifice the stock engine's broad spread of power and excellent mechanical reliability.
To help us achieve these goals, we enlisted the services of Jesse Gatlin, veteran motorcycle drag racer and high-performance engine builder. We asked him to put together a durable, tractable package that would take us to the Nines without requiring a second mortgage on the family homestead.

By the time he was finished, Gatlin had retained most of the GSX-R's stock engine components, a strategy that helped keep costs down and reliability up. He did swap the stock pistons for 80mm (2mm-oversize) MTC forged units, which boost displacement from 1127 to II 86cc and raise the compression ratio from 10.8 to 11.2:1. But he kept the big GSX-R's stock cams, valves and valve springs, along with its original crankshaft and connecting rods.

Gatlin's choice of stock cams was more than an attempt to save a few-bucks; it was a deliberate tuning tactic. Drawing upon the expertise that has made him one of the country's premier motorcycle cylinder-head specialists, Gatlin gave our GSX-R a port job specifically designed to work best with the stock cams. He avoided taking the traditional hot-rodding route, which is to use radical cam profiles and ports that have been hogged-out to the maximum: that approach no doubt could have netted a massive gain in peak power, but it also would have dramatically narrowed the slock motor's ultra-wide

 more moderate power increase throughout the entire rpm range by retaining the stock cam lift and duration, and by judiciously enlarging and reshaping the ports.
Gatlin was quick to point out that air-flow volume alone is not an adequate measure of how well a port works; a properly modified port will also maintain sufficiently high airflow velocity over the range of rpm the engine normally encounters. The ports required to feed a I400cc, 13,000-rpm Pro Stock engine, therefore, are not ideal for a street engine such as our 1186. With that in mind, Gatlin gave our Suzuki a high-velocity porting job that allows the engine to fill its cylinders much more quickly than it otherwise would, thereby precluding the need for high-lift, long-duration cams.

And it works as promised. Since there is no loss of cylinder fill at low rpm (a condition that occurs with long-duration cams because of their late closure of the valves), the powerband on our 1186 is at least as wide as the stock engine's, and much more potent. And the valve gear is as reliable as stock because it is stock . The only thing Gatlin did here was to re-time the stock cams to give the intakes 103-degree lobe centers and the exhausts lOa-degree centers.

We did. however, need to improve upon another intake restriction: the carburetors. Even on the stock engine, the original CV carburetors limit intake flow; on our 1186. they would have been hopelessly restrictive. So, we fitted a set of 40mm Mikuni RS-Series flat-slide carbs. which pass enough air to allow unimpeded flow through the modified ports.

They also offer a wide range of adjustment. Right out of the box. the Mikunis were fairly close, and dialing them in to suit our motor's demands required only lowering the needles to their leanest position, fitting a set of *I35 main jets, and adjusting the accelerator pump to begin its delivery at one-quarter throttle.
On the exhaust side. Gatlin used a pipe of his own design, one that incorporates what he calls a "Tri-Y" header. According to Gatlin, this configuration aids performance at virtually every useful rpm. partly because it maintains high gas-flow velocity, and partly because it manages pressure variations better than traditional 4-into-l systems.

Gatlin also paid particular attention to the combustion-chamber shape, one of the most critical factors in any high-performance engine. He says that the cylinder-head portion of the GSX-R's chamber is superb and needs no modification, but he does slightly reshape the crowns of ihe MTC pistons to work more effi-ciently with his ports and the GSX-R's head. Gatlin says he has found that virtually all aftermarket pistons need to be modified to maintain the efficiency of the stock pistons. He feels that anvone who uses unmodified aftermarket pistons in a GSX-R is likely to encounter severe detonation problems or have an engine that simply runs too hot.

What's more. Gatlin contends thai most hopped-up engines suffer from poor piston-ring seal, and that most aftermarket pistons aren't as good as their stock counterparts in that respect, either. He is a student of the school of thought which professes that pistons should be sized to run in a cvlindcr that has been bored to the piston rings' design diameter. In other words, you bore for optimum piston-ring diameter, not to achieve a specific piston clearance. He prefers MTC pistons because he has found them to be correctly sized for the piston rings, in addition to being lighter than stock-thereby reducing the loads on the connecting rods—and built of an alloy strong enough to promote good long-term reliability.

Cylinder finish also is critical for achieving optimum ring seal, requiring (he bores lo be round and straight lo within a few ten-thousandths of an inch from top to bottom. So. once Gatlin has correctly matched the bores lo the ring diameters, he hones his cylinders to a super-smooth finish. He claims his technique seals the gases in and the oil out of the combustion chambers for as many miles as docs a stock engine's cylinder finish. And lo properly seal the important head-to-cylinder junction. Gailin recommends and sells slock Su/.uki head gaskets—the only kind that never seems to leak oil-that he has modified to accommodate the 2mm-oversizc bores.

Among many other stock components found on our 1186 is the original ignition system. But although it delivers a spark hot enough to ensure reliable ignition, its advance curve is slightly retarded for our engine's requirements. Gatlin easily overcame this shortcoming by installing an adjustable advancer from Dale Walker's Holcshot Performance, which allows the static advance to be set within a 10-degree range. He adjusted ours to provide five degrees more advance than stock.
Gailin had to deal with the stock GSX-RllOO's ignition box, too. It has a built-in rev limilcr thai kills the spark at 11.500 rpm—loo early for our 1186. which develops peak power at about 12,500 rpm and runs strongly lo 13,000.

The simple solution was to install a Suzuki GSX-R750 ignition box. which has a 13.000-rpm rev limiier that leis us lake full advantage of the engine's power potential.
There are. however, a couple of drawbacks to raising the rev limit. One is Ihat the 750's ignition box has a list price of S27I. Another is Ihat the loads on the pistons, rings, rods and bearings are much greater at 13.000 rpm than ihey are ai 11.500. The engine will withstand these addi-lional loads but won't prove as reliable as the stocker unless the GSX-R's original 11.500-rpm redtinc is observed.
Finishing off the powcrtrain package is a Holeshot Performance Electric Power Shifter, which allows fullihroidc, clutchlcss upshifts. A toggle switch turns the shifter on and off so ii can be used only when needed.

We were fully aware, of course, thai our nine-second motor would need the assistance of a nine-second
chassis, since even stock GSX-Rs are wheelie-prone during aggressive dragstrip launches. Under other circumstances, we would have opted for all the usual drag-race modifications—lowering (he chassis, lengthening the swingarm. adding a wheelie bar-to keep the front wheel somewhere near the ground. But the 1186 was intended to be raced only in
streetable trim, which meant that the comparatively small footprint of its DOT tires would significantly limit the available start-line traction. Knowing this, we decided that the only modification needed to insure quick, low-trajectory leaves was to lower the chassis.
We settled on a 2-inch drop at both ends, accomplished at the front by culling a few coils off of each fork leg's main spring, then installing a 2-inch-long piece Of pipe above ihe top-oul spring in each hydraulic damper. The rear end was lowered with a shorter-length shock specially made for us by Fox.
We then ga'vc our GSX-R1186 a custom look by boiling on a complete set of fiberglass body panels from the Body By Northstar division of Northstar Racing. These are near-duplicates of the slock panels, but offer large savings in both cost and weight. A complete Northstar body is six pounds lighter than its stock counterpart: its laminate construction offers

Source Cycle World 1982